Puncture resistant balloon catheter

ABSTRACT

A balloon catheter having an inflatable balloon in which the outer surface of the inflatable balloon is surrounded by an elastomeric sleeve. The sleeve is attached throughout at least a majority of its area to the balloon outer surface to provide pin hole and abrasion resistance. Preferably, the inflatable balloon is made of a flexible material of less elasticity than the material of the elastomeric sleeve. Thus the balloon expands to a generally limited maximum transverse dimension, while the collapse of the balloon is facilitated by the elastomeric sleeve.

This is a division of application Ser. No. 442,568, filed Nov. 29, 1989now U.S. Pat. No. 5,290,306.

BACKGROUND OF THE INVENTION

Balloon catheters are well-known devices in which the catheter carriesan inflatable balloon to occlude and seal a body space, to expand ablood vessel through pressurized inflation of the balloon, or for anyother desired purpose which may typically but not necessarily be atherapeutic purpose in the medical field. In the case of dilatationballoon catheters for angioplasty, for example a PTCA procedure, thecatheter balloon is generally made out of a thin, strong material whichis of relatively low resilience. For example, the catheter balloon maybe made out of biaxially oriented polyethylene terephthalate (PET) or apolyamide material such as nylon. Such strong, flexible materials arecommonly used for angioplasty balloons, and have the advantage that theyare flexible but inelastic so that they can expand outwardly to apredetermined diameter, and then cease further expansion at normalpressures, to avoid damage to the artery wall by over expansion.

One difficulty which is found with such biaxially oriented balloons isthat, since they are typically very thin-walled, they can be easilypunctured through abrasion or the like, even though they have a hightensile strength. Thus, pin holes and ruptures are fairly common whensuch catheter balloons are used in contact with rough surfaces. Also,tiny flaws in the mold of such balloons can create weak spots, since theballoons are so thin-walled. However, it is impractical to increase thewall thickness of these biaxially oriented materials, since then theybecome too stiff, with high flexural moduli, with the result that suchballoons do not collapse properly on deflation to facilitate easywithdrawal from the vascular system of a patient.

Accordingly, there is a need for a balloon catheter in which thecatheter balloon is strong and relatively inelastic, without beingsubject to the formation of pin holes in the molding process, or tearsin the balloon wall through abrasion. At the same time, the balloon muststill be easily collapsible down to a small diameter upon deflation.

Also, there is a need to provide such catheter balloons with an improvedlubricity, or for them to be facilitated to carry a therapeutic agentsuch as an anticoagulant, particularly in the case of angioplastyballoons.

DESCRIPTION OF THE INVENTION

In this invention, a balloon catheter is provided which comprises aflexible, elongated member, an inflatable balloon carried on theelongated member to define an inflation chamber within the balloon, andan inflation conduit extending along the member and communicating withthe inflation chamber.

In accordance with this invention, the inflatable balloon has an outersurface which is surrounded by an elastomeric sleeve. The sleeve isbonded typically throughout at least a majority of its area to theballoon outer surface, to provide pin hole and abrasion resistance.

Preferably, the elastomeric sleeve and balloon are defined as a multiplelayer tube, coextruded together to form a single, integral member of twoconcentric, telescoping layers. It is also preferable for the inflatableballoon to be made of a flexible material which is of less elasticitythan the material of the elastomeric sleeve. Thus, the inflatableballoon, being preferably biaxially oriented polyester such as PET, or apolyamide such as nylon, is flexible but relatively inelastic, to limitthe maximum transverse dimensions of the inflated balloon for reasonssuch as that mentioned above.

The elastomeric sleeve is then provided as an outer layer, and typicallyserves as an aid for the deflation of the balloon once again, after thepressure within the balloon is released. The natural, resilientcharacter of the elastomeric sleeve causes compression of thenon-resilient balloon back to a deflated, minimum-diameter condition,being driven by the natural contraction of the stretched elastomericsleeve back toward its original configuration. Thus, as an advantage ofthe balloon catheter of this invention, the undesirable characteristicof "winging", in which the inflatable balloon collapses on deflationinto an enlarged-width, flat configuration, is reduced or eliminated bythe presence of the surrounding elastomeric sleeve, without creatingundue stiffness in the balloon.

At the same time, any pin holes that may have been formed in theinflatable balloon are sealed by the surrounding elastomeric sleeve, sothat the loss of inflation fluid through the pin hole, if it exists,will be negligible or non-existent. At the same time, the elastomericsleeve serves as an outer protective coating to the balloon, with theelastomeric material being far more resistant to abrasion and roughhandling than the ultra-thin, flexible, inelastic, inflatable balloon.Thus the accidental creation of rips or tears is greatly reduced aswell.

The outer layer of elastomeric material may be made of any elastomer,for example, polyurethanes, polyesterether copolymers, orpolyetheresteramide terpolymers. It is often preferable to select anelastomeric sleeve component which is more compatible with a hydrogelformulation or the like which can serve as a lubricant to the surface ofthe balloon catheter. Thus, a catheter of improved lubricity for ease ofinsertion, typically into the arteriovenous system of a patient, may beprovided if it carries such a hydrogel coating. Materials such aspolyurethane are more compatible to receiving many lubricating hydrogelformulations and retaining it on its surface than are materials such asPET or polyamide.

Additionally, the outer surface of the elastomeric sleeve may carry alayer of material comprising a therapeutic agent or a lubricating agentor both, in a manner similar to the disclosures of Rowe et al. U.S.patent application Ser. No. 322,929 filed Mar. 14, 1989 commonly ownedwith this application.

The elastomeric sleeve may comprise a material having an elongation tobreak of at least 100 percent and a shore `D` durometer of no more thansubstantially 55 to assure that the material is relatively soft. Therelatively inelastic balloon material, however, may have an elongationto break of typically no more than 30 percent. Such materials generallyare substantially stiffer, having a shore `D` durometer of at leastabout 70.

As further modification, the elastomeric sleeve may comprise aformulation which is an intimate physical mixture of, typically, 50 to98 weight percent of a structural plastic material (such as polyurethaneelastomer) and 2 to 50 weight percent of poly(ethylene oxide) or anotherfriction reducing agent. The friction reducing agent can migrate out ofits intimate physical relation with the structural plastic material sothat the elastomeric sleeve serves a double function of the physicalperformance of the elastomeric sleeve as described above, coupled withthe friction reducing performance, which is more fully described inRowland et al. U.S. patent application Ser. No. 345,102, filed Apr. 28,1989 and entitled Hydrophilic Friction Reducing Coating. Commonly ownedwith this application, now U.S. Pat. No. 5,041,100.

If desired, the balloon catheter of this invention may carry anexpansible stent about the outer surface of the elastomeric sleeve, sothat the expansible stent may be expanded by the balloon into engagementwith the wall of a blood vessel. In this and other instances, theelastomeric sleeve may desirably carry an antithrombogenic agent or thelike as more particularly described in the pending Rowe et al.application.

One may inflate and longitudinally stretch a coextruded tube of theballoon and outer elastomeric coating with heat setting, to biaxiallyorient the balloon.

Alternatively, the balloon catheter of this invention may carry aninflatable balloon with an outer, adhering elastomeric sleeve which isnot coextruded as described above, but rather the elastomer may beprovided to the pre-formed balloon as a solvent dispersion. Followingdrying of the solvent dispersion, the elastomer layer is formed.

As another manufacturing alternative, the inflatable balloon may beinflated into pressurized contact with the outer tube of elastomericmaterial, and then heated and biaxially oriented by stretching, with theresult that the balloon also enters into adhering contact with theelastomeric outer tube as it is biaxially oriented.

A PET balloon may be dip coated with a polyurethane elastomer solution.The resultant coating and balloon may have the functional performance ofa PET balloon with the added protection of the polyurethane elastomericlayer. This layer can provide improved scuff and abrasion resistance tothe typically thin-walled balloon, and also the polyurethane outer layermay assist in the collapse of the balloon after deflation, avoiding"winging" and other problems resulting from excessive transversedimensions of the collapsed balloon. Similarly, balloon pin holes aresealed by the polyurethane layer with greatly increased reliability,since a pin hole will only have a negative effect if both layers exhibitaligned pin holes. Separate pin holes in either or both of the layerswhich do not register with each other will generally have no negativeeffect since there can be no significant leakage through the walls uponballoon inflation in that circumstance.

Alternatively, a different biaxially oriented material such as nylon 12may be used as the balloon, with a polyetheresteramide terpolymerserving as the outer elastomeric layer, to achieve advantages similar tothose of the previous embodiment.

It is generally desirable to select elastomeric materials that are atleast somewhat adhesively compatible to the material of which theballoon is fabricated, so that adhesion may be provided between the twolayers.

DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is an enlarged, fragmentary view, taken partlyin longitudinal section, of the distal end of a balloon catheter inaccordance with this invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the drawing, balloon 10 is carried at the distal end of catheter 12,which catheter may be of any conventional design of the prior art exceptfor the modifications specifically disclosed herein. For example, thespecific catheter shown may be used for a conventional PCTA procedure,using balloon 10 to expand the inner diameter of an occluded coronaryartery.

As is conventional, balloon 10 may be made of a cylindrical plasticmember which is typically biaxially oriented, for example PET or nylon.Balloon 10 is sealed at its respective ends 14, 16 to an outer cathetertube 17 and an inner catheter 19, as shown. Inflation lumen 18 may beconventionally provided for fluid inflation and deflation of balloon 10,being a space between outer catheter tube 17 and inner catheter 19.Inner catheter 19 may or may not carry one or more catheter lumens, asmay be desired. Additionally, catheter 12 may carry electrodes andelectrical conductors extending the length thereof for purposes ofpacing or sensing of coronary action, if desired.

If desired, means for venting air from catheter balloon 10 may beprovided.

The wall thickness of balloon 10, when made of biaxially oriented PET,may be about 0.0005 inch. Catheter 12 and catheter tubing 17 may each bemade of a polyester such as DuPont Hytrel. Balloon 10 may be sealed tocatheter 12 and catheter tubing 17 at its respective ends with anadhesive or by a heat sealing process in a conventional manner.

In accordance with this invention, balloon 10 comprises the inner layerof a co-extruded tubing, with the outer tubular layer 20 thereofcomprising a polyurethane elastomer, may of which are commerciallyavailable and used in the manufacture of catheters.

Coextruded polyurethane elastomer outer layer 20 is bonded through thecoextruded manufacturing process to the inner PET balloon layer 10.Outer polyurethane layer 20 may have a thickness of, typically, 0.0005to 0.002 inch, to provide abrasion and puncture resistance to thecoextruded tubular structure 22 which comprises PET balloon 10 andpolyurethane outer tubular layer 20. The polyurethane elastomer layer 20is substantially more soft and elastic than the PET balloon layer 10.The PET balloon 10 generally expands to a fully expanded configurationand then greatly resists further expansion at even substantiallyincreased internal pressures. However, the elastomeric layer 20stretches outwardly upon such expansion, and thus provides atransversely collapsing bias to balloon 10 upon deflation. Despite theincreased wall thickness provided by outer layer 20, the tubular balloonstructure 22 retains the desired characteristics of a biaxially orientedPET balloon without excessively increased stiffness upon deflation.Outer elastomer layer can compress inner balloon 10 upon deflation, asthe outer elastomeric layer collapses back towards its normal,unstressed configuration following balloon inflation, to assist in adesired, complete collapse of the balloon structure 22.

If desired, a third hydrogel layer 24 may be provided to balloonstructure 22, to serve as a lubricant for insertion of the catheter.This layer also may be very thin, typically 0.0001 to 0.0005 inch. Layer24 may also include a therapeutic agent such as an anticoagulant.

The above has been offered for illustrative purposes only, and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

That which is claimed is:
 1. A balloon catheter, which comprises aflexible, elongated member, an inflatable balloon carried on theelongated member to define an inflation chamber within said balloon, aninflation conduit extending along said elongated member andcommunicating with the inflation chamber, said inflatable balloon beingmade of a flexible, relatively inelastic plastic essentially free ofholes and having an outer surface surrounded by an elastomeric sleeve,said sleeve being bonded throughout at least a majority of its area tosaid balloon outer surface to provide pin hole and abrasion resistance.2. The balloon catheter of claim 10 in which said inflatable balloon ismade of a flexible material of less elasticity than the material of saidelastomeric sleeve.
 3. The balloon catheter of claim 10 in which saidelastomeric sleeve and said balloon are together defined by a coextrudedtube.
 4. The balloon catheter of claim 3 in which the outer surface ofsaid elastomeric sleeve carries a layer comprising a therapeutic orlubricating agent.
 5. The balloon catheter of claim 1 in which saidinflatable balloon comprises a continuous, non-fibrous plastic tube. 6.A balloon catheter, which comprises:a flexible, elongated member; aninflatable balloon carried on the elongated member; an inflation chamberdefined within said balloon; an inflation conduit communicating with theinflation chamber; said inflatable balloon being made of a firstflexible plastic material; and a second, different plastic materialco-extruded with said first plastic material for providing pin holeand/or abrasion resistance to said first plastic material.
 7. A ballooncatheter as defined by claim 6, said second plastic material havinggreater flexibility than said first plastic material.
 8. A ballooncatheter as defined by claim 6, said second plastic material havinggreater elongation than said first plastic material.
 9. A ballooncatheter as defined by claim 6, said first plastic material comprisingnylon.
 10. A balloon catheter as defined by claim 6, said second plasticmaterial comprising an elastomeric material.
 11. A balloon catheter asdefined by claim 6, said second plastic material being more elastic thansaid first plastic material.
 12. A balloon catheter as defined by claim6, said second plastic material being more resistant to pin holes thansaid first plastic material.
 13. A balloon catheter as defined by claim6, said second plastic material being more resistant to abrasion thansaid first plastic material.
 14. A balloon catheter as defined by claim6, in which said second plastic material overlies said first plasticmaterial.
 15. A balloon catheter, which comprises:a flexible, elongatedmember; an inflatable balloon carried on the elongated member; aninflation chamber defined within said balloon; an inflation conduitcommunicating with the inflation chamber; said inflatable balloon beingmade of a first flexible, relatively inelastic biaxially orientedplastic material; and a second different plastic material co-extrudedwith said first plastic material for providing pin hole and/or abrasionresistance to said first plastic material.
 16. A balloon catheter whichcomprises a flexible, elongated member, an inflatable balloon carried onthe elongated member to define an inflation chamber within said balloon,and an inflation conduit extending along said member and communicatingwith the inflation chamber, said inflatable balloon being made of aflexible, relatively inelastic biaxially oriented plastic essentiallyfree of holes and having an outer surface surrounded by an elastomericsleeve, said sleeve being bonded throughout at least a majority of itsarea to said balloon outer surface to provide pinhole and abrasionresistance.
 17. A balloon catheter which comprises a flexible, elongatedmember, an inflatable balloon carried on the elongated member to definean inflation chamber within said balloon, and an inflation conduitextending along said member and communicating with the inflationchamber, said inflatable balloon being surrounded by an elastomericsleeve to provide pinhole and abrasion resistance, said balloon andsleeve being together defined by a co-extruded tube, said balloon beingmade of a flexible, relatively inelastic biaxially oriented plasticmaterial.
 18. A method of forming a balloon catheter comprising aflexible, elongated member carrying an inflatable balloon, comprisingthe steps of:providing a first flexible plastic material; providing asecond, different plastic material; and co-extruding said first andsecond plastic materials to form said inflatable balloon with saidsecond plastic material serving to provide pinhole and/or abrasionresistance to said first plastic material.
 19. A method of making aballoon catheter comprising a flexible elongated member carrying aninflatable balloon, the method steps comprising:providing a flexible,relatively inelastic biaxially oriented plastic essentially free ofholes; applying to said biaxially oriented plastic an elastomeric sleeveto provide pinhole and abrasion resistance.
 20. A method of forming aballoon catheter comprising a flexible elongated member carrying aninflatable balloon, which comprises the steps of:providing a firstflexible plastic material; providing a second, different plasticmaterial; co-extruding said first flexible plastic material with saidsecond, different plastic material to form a co-extruded tube; andstretching the co-extruded tube to orient the balloon material.
 21. Amethod of forming a balloon catheter comprising a flexible, elongatedmember carrying an inflatable balloon, comprising the steps of:providinga first plastic material; providing a second, different plasticmaterial; and co-extruding said first and second plastic materials andforming a triple layer balloon.
 22. A method of forming a ballooncatheter comprising a flexible, elongated member carrying an inflatableballoon, comprising the steps of:providing a plurality of plasticmaterials; and co-extruding said plastic materials and forming a triplelayer balloon.
 23. A method of forming a balloon catheter comprising aflexible, elongated member carrying an inflatable balloon, comprisingthe steps of:providing a first plastic material; providing a second,different plastic material; co-extruding said first and second plasticmaterials; and inflating and stretching the plastic materials to form abiaxially oriented triple layer balloon.
 24. A method of forming aballoon catheter comprising a flexible, elongated member carrying aninflatable balloon, comprising the steps of:providing a plurality ofplastic materials; co-extruding said plastic materials; and inflatingand stretching the plastic materials to form a biaxially oriented triplelayer balloon.
 25. A catheter for medical purposes, said cathetercomprising:a tubular member having a distal end and at least one lumendisposed therethrough; a balloon having at least one open end, said openend being sealed at a joint to said distal end, the interior of saidballoon being in communication with said lumen, said balloon having anelongated tubular body and comprising a plurality of co-extruded layersof different polymeric materials, at least one of said layers being apolymer that is sealed by heat to said tubular member.
 26. A catheterfor medical purposes, said catheter comprising:a tubular member having adistal end and at least one lumen disposed therethrough; a balloonhaving at least one open end, said open end being sealed at a joint tosaid distal end, the interior of said balloon being in communicationwith said lumen, said balloon having an elongated tubular body andcomprising a plurality of co-extruded layers of different polymericmaterials, at least one of said layers being a base structural layer andthe other of said layers being formed of a polymer which will make theballoon more resistant to abrasion and pinhole formation.